This invention relates generally to a socket used in conducting electrical tests of semiconductor (SC) devices and more particularly to a socket for removably receiving a semiconductor device, such as an integrated circuit, and making electrical contact between the contacts of the device and respective contacts or terminals of the socket which in turn are connected to respective contact pads of a circuit substrate.
It is conventional to place a semiconductor device in a socket which, in turn, is connected to a circuit substrate and then to place the substrate into an oven so that the temperature and voltage of the semiconductor device can be raised to a selected level to conduct a stress test, called a burn-in test, to determine whether the semiconductor device meets the required manufacturing specifications.
Typically, prior art sockets used for this purpose comprise a base member formed of electrically insulative material in which an electrical contact element is mounted for each contact of the semiconductor device to be tested. The contact elements are arranged in a selected pattern relative to the semiconductor device mounting seat provided in the base and have contact portions adapted to be placed in electrical engagement with respective contacts of the semiconductor device. In one type of prior art socket the semiconductor device to be tested is placed in the semiconductor device receiving seat and a cover member, pivotably mounted to the base, is held in a closed position by means of a spring biased latch, a clip, a nubbin on an actuation arm or base, a protrusion or the like. The cover places a bias on the semiconductor device to provide a selected contact force between the device leads and the contact elements of the socket. When a semiconductor device is loaded into the socket for testing it is critical that the cover be maintained in the closed position for the duration of the test procedure, however, in typical prior art structures either the cover locking mechanism is cumbersome and time consuming to apply, such as a clip, or it is subject to accidental dislodgement with consequent unintended and untimely opening. Another problem associated with this type of socket having a pivotably mounted cover relates to the angled application of force to the semiconductor device sometimes causing damage to the semiconductor device. That is, due to the pivoting movement of the cover, typically the upper inside edge of the semiconductor device closest to the pivotable connection of the cover to the base is the first portion of the device to engage the cover and it receives a force the direction of which changes as the cover is pivoted until the bottom surface of the cover comes into a parallel position with the top surface of the semiconductor device. This angled force, i.e., force which is not normal to the top of the SC, can damage the SC device.
It is an object of the present invention to provide a socket which overcomes the above noted limitations of the prior art. Another object of the invention is to provide a socket having a pivotably mounted cover which has a locking mechanism for maintaining the cover in the closed position which is simply and quickly locked and unlocked and yet which is not subject to accidental or unintended unlocking. Another object of the invention is the provision of a socket having a pivotably mounted cover which avoids damaging semiconductor devices loaded therein. It is a further object of the invention to provide a socket which is highly reliable in operation and economical to manufacture.
Briefly, a socket made in accordance with a first embodiment of the invention comprises a cover pivotably mounted to a base to enclose a semiconductor device removably received for testing purposes. A locking mechanism for maintaining the cover in the closed position during the testing procedure includes a locking pin extending laterally from the base which interacts with an over center linkage mechanism. The linkage mechanism includes a first handle link pivotably mounted on the cover, providing a first axis immovable relative to the cover, a second locking link rotatably mounted to the cover having a locking pin receiving catch at one end thereof and having another end pivotably connected to an end of a third interconnecting link providing a second axis movable relative to the cover and with another end of the third link pivotably connected to the first link providing a third axis movable relative to the cover. When the cover is pivoted toward the closed position with the handle of the first link extending away from the cover, the first link is pivoted toward the cover bringing the locking pin receiving catch into engagement with the locking pin and the end of the cover frame into engagement with the locking pin bar and continued pivotal motion results in the third movable axis moving with snap action from one side of an imaginary line extending between the first and second axes to the other side thereof to thereby securely lock the cover in the closed position. Over center movement is limited by engagement of the second locking link with the first handle link. In a modified embodiment, the locking pin is attached to the second locking link and a locking catch member is pivotably mounted on the base for interaction with the locking pin. In this embodiment the cover can be opened either by raising (pivoting) the first handle link for manual operation or by applying a force to the pivotably mounted locking catch member.
In one embodiment the cover is integrally formed with a heat sink while in another embodiment a separately formed heat sink is independently mounted on the cover for sliding movement through a heat sink receiving aperture formed in the cover. According to a feature of the latter embodiment, the heat sink is preferably mounted on the cover with a first spring connection adjacent the hinged end of the cover and with second and third spring connections on the opposite end of the cover to ameliorate an even application of force to a semiconductor device disposed in the semiconductor receiving seat of the base. According to another feature of an embodiment of the invention, a boss having an outer configuration generally matching but preferably slightly less than that of a die of a semiconductor device to be received in the socket extends downwardly from the heat sink for engagement with a semiconductor device received in the socket. According to yet another feature, one or more pressure bars are slidably mounted for flexible movement in a pair of slots in the bottom surface of the cover for engaging the outer portions of the semiconductor device received in the socket.
In a modified embodiment the bottom surface of the heat sink is provided with a recessed portion for use with semiconductor devices having packaging features which extend above the die portion(s) and/or to move the initial engagement of the heat sink with the semiconductor device to a location slightly inboard of the outer periphery of the SC die.